@cleitonevil You could have just said "that doesn't have a sibling," because by your definition the Ninomiyas don't exist in this manga. It's a younger sister/older brother pair.
Also, is everyone so desensitized to ridiculousness that no-one is mentioning the magic ice cream that somehow unbuttoned and opened her shirt before landing between her breasts? 🤣
Yet, huh? So, you're going to think about it at some point? Oh, lemme guess, you're going to decide on twins. Just keep the twincest chain going. I approve of that desire.